title: Interaction of 5-ethynyl-2'-deoxyuridylate with thymidylate synthetase.
abstract: The interaction of 5-ethynyl-2'-deoxyuridylate (5-ethynyl-dUMP; 1) with thymidylate (dTMP) synthetase has been investigated. The compound was an inhibitor of the enzyme, competitive with 2'-deoxyuridylate (dUMP) when the reaction was initiated by addition of enzyme (Ki = 2.7 X 10(-6) M). However, upon preincubation of 1 with dTMP synthetase, the inhibition pattern became noncompetitive. The time course of the enzyme reaction in the presence of 1 was nonlinear, indicating an increase in binding with time. Irreversible inactivation of the enzyme did not occur. The compound did not appear to become altered structurally as a result of interaction with the enzyme. A ternary complex was formed among dTMP synthetase, compound 1, and 5,10-methylenetetrahydrofolate, which was stable enough to survive Sephadex G-25 filtration but dissociated upon denaturation of the enzyme.
mesh_terms: D001667:Binding, Competitive; D055598:Chemical Phenomena; D002621:Chemistry; D003856:Deoxyuracil Nucleotides / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D007780:Lacticaseibacillus casei / Q000201:enzymology; D008780:Methyltransferases / Q000037:antagonists & inhibitors*; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D003856:Deoxyuracil Nucleotides; C033258:5-ethynyl-2'-deoxyuridylic acid; D008780:Methyltransferases; D013940:Thymidylate Synthase